The current process for crystallizing CL-20 uses chloroform to precipitate CL-20 from ethyl acetate. Chloroform and ethyl acetate cannot be effectively separated by distillation for reuse which results in the continual discharge of a chlorinated waste stream. It is harmful to the environment and economically wasteful to continually discharge a chlorinated organic solvent such as chloroform. As a chlorinated solvent, chloroform may potentially contribute to ozone depletion. Thus, it would be an advancement in the art to provide a process for crystallizing CL-20 which does not require or discharge chlorinated solvents and which permits efficient recycling of the solvent within the crystallization process.
A great number of skilled workers in the art have attempted to use non-chlorinated solvents in crystallizing CL-20. But only chloroform has consistently and reproducibly produced the desirable .epsilon.-polymorph of CL-20.
In addition, other current CL-20 crystallization techniques do not consistently produce high quality CL-20. CL-20 is known to have several different crystal polymorphs, one of which is a high density phase referred to herein as the .epsilon.-polymorph. CL-20 produced according to prior art techniques is predominantly a low density crystal polymorph, referred to herein as the .alpha.-polymorph. .epsilon.-polymorph CL-20 possess superior ballistic properties compared to the commonly formed .alpha.-polymorph. The crystallization conditions which produce .epsilon.-polymorph CL-20 are not well understood in the art; therefore, it would be an advancement in the art to provide a process of crystallizing CL-20 which produces predominantly .epsilon.-polymorph CL-20.
Such processes for crystallizing CL-20 are disclosed and claimed herein.